The invention relates to a hydraulic circuit for operating a tool especially of a construction equipment like e.g. an excavator, crane, wheel loader, drilling machine, grass cutter or others. Furthermore, the invention relates to a control unit and a method for controlling the hydraulic circuit and to a construction equipment comprising such a hydraulic circuit.
If a tool which is mounted at a construction equipment is exchanged by another tool, the operator of the construction equipment has to change and adjust accordingly the hydraulic parameter settings of the construction equipment like the pressure, the flow, the operation mode and other parameter settings which are specifically required for operating the new tool. This is usually very time consuming and implies the risk that inappropriate settings are selected by the operator.
It is desirable to provide a hydraulic circuit and a method for operating a hydraulic circuit by which this time consuming task is substantially reduced and the related risk is substantially reduced as well.
It is desirable to provide a hydraulic circuit which is simple in construction and enables to be controlled with an electronic control unit in a comparatively simple way.
According to an aspect of the invention, a hydraulic circuit is provided and, according to another aspect of the invention, a method for operating a hydraulic circuit is provided. One of the advantages of aspects of the invention is that an operator of the construction equipment is offered a high flexibility to realize settings for a plurality of different tools in an easy and quick manner.
More in detail, these solutions offer a flexible way to set and control the hydraulic circuit in a construction equipment. This is achieved especially by the fact that the settings and operating parameters of a nearly unlimited number of different tools can be programmed and stored, and then a certain tool which has been connected to the construction equipment can easily be selected by the operator, and the hydraulic parameter settings of the construction equipment for this tool can be adjusted in a quick and easy manner.
This is true for very different kinds of tools. For example, a toggle function can be realized on a related tool in an easy way. For example, a tool in the form of a hammer can be operated by the hydraulic circuit as long as a related button is pressed “on”. Furthermore, for operating a related proportional tool, e.g. a proportional and progressive roller switch or a proportional foot pedal can be used in order to generate an accordingly increasing hydraulic flow or hydraulic pilot pressure for actuating the tool.
Another advantage of aspects of the invention is that a proportional foot pedal valve for the tool control can be easily included in order to keep a maximum flow limitation in both directions of the pilot pressure, wherein a de-activation function of the hydraulic circuit is kept, i.e. even if the pedal is pressed in order to operate a tool, the hydraulic circuit can be de-activated, if necessary, by means of the first proportional valve by switching the same such that substantially no hydraulic pressure is applied at its output.
Furthermore, a progressive and proportional control of the output flow of the hydraulic circuit is provided, for which only one PWM (Pulse Width Modulation) output from the control unit or ECU (Electronic Control Unit) is necessary.